KatMouse: http://ehiti.de/katmouse/Allows you to scroll windows with wheel by moving mouse over it BUT without it being "in focus" (not clicking on it)...-----Quoted the above from a lifehacker comment. Maybe it is what you are looking for?

KatMouse: http://ehiti.de/katmouse/Allows you to scroll windows with wheel by moving mouse over it BUT without it being "in focus" (not clicking on it)...-----Quoted the above from a lifehacker comment. Maybe it is what you are looking for?

Not elegant, but if you want to type in the inactive window, I think you are going to have to save the status of the active window, make the window under the cursor the active window, type or have the typed text pasted, and then restore the original active window.

I can think of a few ways to trigger the procedure, but I don't understand how this will work without three hands (one to position the mouse, and the other two to type). Or is it one hand typing while the other is mousing?

If I understand correctly what you mean, this is a contradiction in terms. A clicked window will receive focus - it's one of the most basic rules of Windows user interface. Conversely, a window that has no focus does not accept input (clicking, typing) - Windows does not send mouse or keyboard messages to an inactive window. And only one window can have focus and receive input at any given time.

Programs like KatMouse work by "manually" sending appropriate scroll messages to a window underneath the mouse. I guess a similar program could send clicks too, but sending a click would activate the window.

While it's also possible to send keyboard messages (though trickier and not all key combinations can be sent reliably), I'm not sure if inactive windows process keyboard messages, and you could not use the physical keyboard to do so, because your physical keypresses would go to the currently active window.